Listen to Robert Emmerich introduce The Big Apple, a hit song from 1937. Music written by Bob and performed by Tommy Dorsey's Clambake Seven with Bob on piano. Lyrics written by Buddy Bernier and sung by Edythe Wright. Audio provided by Dorothy Emmerich.

The “mess box” is a pantry that old-time cooks had attached to the rear or their “mess wagons.” A “mess wagon” was also called a “chuck wagon,” and its corresponding item was called a “chuck box.” The mess box often folded down, forming a table in the rear of the wagon.

(Oxford English Dictionary)
mess box U.S., a box in which food and kitchen utensils are carried.
1859-60 in Dict. Amer. Eng. (1942) III. 1511/2 We had what we call a *mess box which contained all our cooking utensils.
1885 Overland Monthly Apr.-May 389/2 The dishes put away in the mess box on the back end of the wagon, a timid kind of foraging tour is made.
1921 in N. H. Thorp Songs of Cowboys (ed. 2) 24 The way we gathered round that mess-box, scramblin’ for tools, Showed the disregard for ethics that is taught in other schools.

(Dictionary of American Regional English)
mess box n chiefly West
A chest or box in which cooking and eating utensils and food are carried.
1859-60 Mrs. Witter Letters (MS.) 3 (DAE), we had what we call a mess box which contained all our cooking utensils.
1884 Shepherd Prairie Exper. 138 West, A mess-box was fixed into the hind-end of the waggon.
1890 D’Oyle Notches 26 (DAE at chuck wagon), The sun blistered the paint upon the “mess box” behind the “chuck-waggon.”
1894 Harper’s New Mth. Mag. 89.515, He now returned to Captain Glynn and shared his mess-box.
1910 in 1914 Stewart letters 106 WY, Early one morning we started with a wagon and a bulging mess-box for Zebbie’s home.
1913 (1979) Barnes Western Grazing 116 SW, One can still find the old-time “chuck wagon” and the great mess box with its hospitable lid and cranky cook.
1921 Thorp Songs Cowboys 24 CO, The way we gathered round the mess-box, scramblin’ for tools,/Showed the disregard for ethics that is taught in other schools.

Google BooksA Visit to Salt Lake
by William Chandless
London: Smith, Elder, and Co.
1857
Pg. 53:
The volley of Anglo-Italian oaths from the old Italian, as his team, instead of coming out, turns hopelessly back into corral; and then “Maledetto! malaedetto!” from half a dozen mellifluous voices, as every off steer of the afore-mentioned team successively runs his head against the Italian mess-box behind one of the waggons, ending in an upset and a conglomeration of frying-pans, coffee-mill, bacon, flour, green and brown coffee, fallen together on the ground.

Google BooksPioneer Biography:Sketches of the Lives of Some of the Early Settlers of Butler County, Ohio
by James McBride
Volume I
Cincinnati, OH: Robert Clarke & Co.
1869
Pg. 255:
While his servants were preparing supper, the General drew off his boots and seated himself on a mess-box, with his elbows resting on his knees, holding a wet sock in each hand, which he was endeavoring to dry by the fire.

14 August 1878, Iowa State Reporter (Waterloo, Iowa), “A Wagon Trip to the Mountains and Camp Life in Colorado,” pg. 2, col. 1:
On the morning of Monday, the 8th day of July, ‘78, we filled our mess box, piled into the great lumber wagon a cooking stove made of sheet-iron, bedding, tent and camp stools.

4 July 1885, Decatur (IL) Daily Republican, “Range Riding: Stirring Scenes of the Season in the Montana Cow Camps,” pg. 2, col. 3:
And now a few words regarding the “mess” of the cow-camp. The cooks and cookees take charge and drive the mess-wagons, with their camp equipment, from place to place during the round-up periods. Almost invariably the cooks are professionals, and the cooking is excellent. With delicious, juicy Montana beef, with bread made from Dakota wheat, and with many of the vegetables and fruits supplied by the “canners,”—all prepared, usually, in a manner to suit the most particular tastes,—the meals, whether spread upon the green grass or upon the tables made by letting down the doors of the mess wagon mess-boxes are, as a rule, greatly relished by all who try them., and are far more satisfying than the dinners of many a first-class hotel.—Miles City Cor. Chicago Tribune.

Google BooksPrairie Experiences in Handling Cattle and Sheep
by Major W. Shepherd
London: Chapman and Hall
1884
Pg. 221:
If then the wagon comes within reach they ransack the mess box, and supplement three hearty meals by an extra lunch.

27 July 1901, Kansas City (MO) Star, “Everything Campers Need Sleeping Berthe Lockers and a Model Mess Box in the Rear of Their Wagon,” pg. 5:
The rear end of the wagon, from top to bottom, is allotted to the mess. Here all the cooking paraphernalia is placed, together with all the stores of the party that do not require to be kept in a particularly cool place.
(...)
At meal time the cover of the mess box at the rear end of the wagon is brought down to a horizontal position, being supported on either side by chains reaching from the wagon top, down, this forming a table of comfortable proportions. The mess box exposed by the letting down of the cover, forms a model sideboard for camping. It is big enough to contain all necessary stores for six people for at least three weeks, excepting eggs, dairy products and fresh meat, which are procured along the route.

Google BooksThe Cowboy at Work
by Fay E. Ward
New York, NY: Hastings House
1958
Pg. 37:
The chuck wagon, or mess wagon, is an ordinary lumber wagon in which is installed a mess-box, or chuck-box, set in the rear end of the wagon-box as shown in the illustrations on Plate 9.